Machine for slitting the bark of logs



April 22, 1958" P. AVARD MACHINE FOR SLITTING THE BARK OF LOGS 2 Shets-Sheet 1 Filed Feb. 25, 1957 INVENTOR Paul AVA RD AT TORMEYS' April 22, 1958 P, AVARDQ MACHINE FOR SLITTING THE BARK 0F LOGS Filed Feb. 25, 1957 2 Sheets-Sheet 2 INVENTOR Paul AVARD ATTORNEYS United States Patent-.0

MACHINE FOR SLITTIN G THE BARK F LOGS Paul Avard, Cap Rouge, Quebec, Canada Application February 25, 1957, Serial No. 642,257

1 Claim. (Cl. 144-436) The present invention relates to a machine for slitting the bark of logs and, more particularly, to a machine of the character described for carrying out the method of debarking logs disclosed in applicants co-pending application Serial No. 642,258 of even date.

In accordance with the invention described in the above noted co-pending patent application, it has been found that debarking of logs is greatly facilitated if the logs are slit along their entire length down to the wood. When such slits are made, the peripheral tensional stress normally existent in the bark causes the bark to contract peripherally of the log, thereby starting destruction of the bond existing between the bark and wood. Thereafter, when the logs are subjected to the action of atmospheric elements such as air, rain, ice and bacteria, the bark becomes practically completely detached from the wood of the log. This may be explained by the fact that water can penetrate through the slits and saturate the cork-like part between the bark proper and the wood and activate the disintegration of said cork-like part; thereafter air easily penetrates and facilitates the action of bacteria for further destroying the bond between the bark and the wood and also promotes the drying of the bark.

As mentioned in said aforesaid co-pending application, the method is applicable for debarking pulp wood logs as well as logs for lumber and logs from dead trees.

The main object of the present invention is the provision of a machine for carrying out the slitting operation ofthe logs in accordance with the above noted method.

Another important object of the present invention is the provision of a portable machine of the character described which may be carried in the woods so as to effect the slitting operation as soon as possible after the trees have been felled.

Still another object of the present invention is the provision of a machine of the character described more particularly adapted to be used in conjunction with a log conveyor system. 1

Another important object of the present invention is the provision in a machine of the character described of means to positively limit the depth of cut in the bark so as to prevent damaging the wood.

The foregoing and other important objects of the present invention will become more apparent during the following disclosure and by referring to the drawings in which:

Figure 1 is a perspective view of a first embodiment of the machine according to the present invention;

Figure 2 is a perspective view of a log being slit by a machine in accordance with a second embodiment of the present invention;

Figure 3 is a perspective view of the second embodiment;

Figure 4 is a cross-section of the cutting head provided with an outer sleeve, taken along line 4-4 of Figure 3;

Figure 5 is a cross-section of a similar cutting head but without the outer sleeve;

Figure 6 is an'exploded perspective view of the outer sleeve, ball bearing element and internal sleeve which,

are parts of the cutting head of Figure 4; and

Figure 7 is a partial plan view of a preferred form of a circular saw used in the machine according to the present invention.

Referring now more particularlyto the'drawings in,

which like reference characters indicate like elements throughout, Figure 1 shows part of a conventional conveyor system, generally indicated by reference numeral 1, and having a conveyor chain 2 provided at spaced'intervals therealong with means (not shown) for engaging the trailing end of the logs in order to positively movej the same along the conveyor in the direction of arrow 3. Two upright members 4, disposed on each side of the conveyor 1, supportthereover a cross member 5 which is at such a height as to clear the logs L passing thereon the transverse mernber 5 and is pivoted on a driving shaft 7 which passes under. A gear box 6 is arranged therethrough and is journ alled therein. The driving shaft is supported on member 5 by brackets 7 to the driving shaft 7 by means of suitable gearing (not in the gearbox 6. ,Pivotal movement of 7 shown) housed the gear box 6 about the driving shaft 7 will cause swinging movement of the arm 12 in a substantially vertical plane passing through the centre line of the conveyor chain 2. The arm 12 supports at its outer end a cutting head C provided with a circular saw 25.

Referring to Figures 4 to 6, the outer end of the tubular arm 12 is secured to a casing 13 and the transmission shaft enters said casing and is provided with a bevelled pinion 14 in meshing engagement with a bevelled pinion 15, the latter being secured to a transverse shaft 16 which is journalled in bearings 17 and 18 supported within the casing 13.

I The transverse shaft 16 has an enlarged portion 19 proectmg outwardly of the housing 13 and which is terminated by -a screwed portion 20 of reduced diameter for receiving a nut 21 and washer 22. Intermediate the portions 19 and 20 there is formed a triangularly shaped portion 23 for engaging a triangular opening 24 of a circular saw 25 which is secured in position by nut 21.

The enlarged portion 19 is adapted to tightly fit within an inner sleeve member 26 having at its outer end a radially, outwardly projecting fiange 27 adapted to abut the circular saw 25. The sleeve 26 is adapted in turn to engage the inner ring 28' of. a ball bearing 28, the outer ring 28 of which is adapted to tightly fit an outer metal sleeve 30.

The relative external diameters of the outer sleeve 30 and of the circular saw 25 are chosen in relation to the thickness of the bark B of the log L to be slit. The outer sleeve 30 is adapted to roll in frictional engagement with the outside surface of the bark of the log to be slit and will follow all the irregularities of said outer surface of the log, thereby providing for uniform depth of cut of the circular saw 25. The depth of cut is regulated so as to completely slit the bark but to only make a very sha1- low cut in the wood. This is easily accomplished due to the fact that, generally speaking, the bark of logs of a given tree species is substantially uniform in thickness.

In order to keep the fibers of the wood as intact as possible, the saw 25 is chosen with teeth T of the type shown in Figure 7. The teeth T have a front edge T rearwardly and is rotated in the direction of arrow 7" by a suitable motor, such inclined from tip to root with respect to a radius passing through the tip.

The gauge of the outer sleeve 30 is selected in accordance with the diameter of the circular saw chosen and the thickness of the bark. If a small circular saw 25 is used, as shown in Figure 4, the outer sleeve 30 may not here quired, in which case the outer ring 28 of the ball bearing 28 contacts the bark Bof the log L.

Referring to Figure l, the driving shaft 7, while rotating the saw-25, also tends to press said saw against the log, while allowing for irregularities in the outer surface of said log. The saw 25 will preferably rotate at a high speed'and the log L is moved longitudinally by the conveyor. Therefore, a straight slit 31 will be made by the saw 25 in the bark of the log L rnoving underneath the transverse frame 5. The swinging movement of the arm 12 will allow for variations of the diameter of the various logs successively slit by the saw 25.

According to another embodiment of the present invention, the arm 12'and cutting head C may be directly connected to a portable gasoline engine M which is preferably ofthe type used for. chain saws. A portable unit of this type allows logs L to be slit at the site where the trees are felled.

While preferred embodiments according'to the present invention have beenillustrated and described, it is under-' stood that various modifications may be resorted to without departing from the spirit and scope of the appended claim.

I claim: a

An apparatus for making longitudinal slits in the'bark of logs comprising, in combination, a conveyor system for moving said logs axially in a predetermined path, a frame structure straddling and extending over said conveyor system so that said logs will pass underneath said structure, a driving shaft journalled on said structure, power means connected to said driving shaft, a gear box pivoted on said driving shaft and supported thereby, a tubular arm secured to said gear box for swinging movement in a plane passing substantially through the centre line of said conveyor system, a casing secured to the outer end of said arm, a transverse shaft journalled within said casing, said transverse shaft projecting. from one end of said casing, means to secure a circular saw to said projecting end of said transverse shaft spacedly from said casing, an inner sleeve fitted on said shaft intermediate said casing and said saw and having a. radial flange abutting said circular saw, a ball bearing mounted on said inner sleeve, an outer sleeve mounted on the external ring of said ball bearing, the external diameter of said outer sleeve being less than the effective diameter of said circular saw so as to provide guiding means to regulate the depth of cut of said circularsaw, and power transmission means between said driving shaft and said transverse shaft.

References Cited in the file of this patent UNITED STATES PATENTS 442,657 Woodside ec. 16, 1890 704,373 Rawson July 8, 1902 938,135 Fellows Oct. 26, 1909 1,797,646 Gardner Mar. 24, 1931 2,478,807 Critchfield Aug. 9, 194-9 2,697,457 Lawrence Dec. 21, 1954 FOREIGN PATENTS v 36,840 Norway Feb. 19, 1923 

